Now that we have learned compilation using command line interface, let
us introduce Makefiles. To compile exactly the same way as we have
compiled so far, a very simple Makefile (incomplete but still
functional) would be as under.

When we introduced target greeting_en in line no. 1, line
nos. 2 and 3 describe what has to happen when someone invokes
make greeting_en. It may not be visible to naked eyes, but
it is very important that those lines have to start with a TAB.